1. Field of the Invention
The present invention relates to a semiconductor device and a method of manufacturing the same, and more particularly, to an analog capacitor and a method of manufacturing the same.
2. Description of the Related Art
Merged memory logics (MML) are emerging devices in which a memory cell array part, for example, a dynamic random access memory (DRAM), and an analog circuit or a peripheral circuit are integrated together within one chip. Introduction of the MML has resulted in great improvements to multimedia functions and has allowed highly integrated high-speed semiconductor devices.
In analog circuits requiring high-speed operation, a semiconductor device having a large capacity capacitor is under development.
Generally, in a case where a capacitor has a polysilicon-insulator-polysilicon (PIP) structure, since an upper electrode and a lower electrode are formed of conductive polysilicon, oxidation occurs at an interface between the upper electrode and a dielectric thin film or an interface between the lower electrode and the dielectric thin film so that a native oxide layer is formed. This results in a decrease in the total capacitance of the capacitor. Further, the capacitance of the capacitor is decreased due to a depletion region formed in a polysilicon layer. Thus, the PIP structure is not desirable for semiconductor devices requiring high-speed and high-frequency operations.
In order to solve this problem, the structure of the capacitor has been changed into a metal/insulator/silicon (MIS) structure or a metal/insulator/metal (MIM) structure. Having low specific resistance and no parasitic capacitance due to depletion, an MIM-type capacitor is usually used for a high-performance semiconductor device.
An analog capacitor having an MIM structure according to the prior art includes a lower electrode and an upper electrode which are formed of TiN and a dielectric layer which is located between the lower electrode and the upper electrode and is formed of HfO2 having a high dielectric constant.
Generally, as the size of semiconductor devices becomes smaller, the thickness of the dielectric layer of the capacitor must be reduced to ensure sufficient capacitance of the capacitor. However, when the thickness of the dielectric layer is reduced, as a voltage applied to the dielectric layer through the lower electrode and the upper electrode changes, the capacitance of the dielectric layer changes. The greater the change in capacitance of the dielectric layer according to the applied voltage, the worse the precision of an analog circuit. Thus, in order to maintain uniform capacitance and a leakage current characteristic, it is necessary to develop a thin-film capacitor and a material suitable for forming the thin-film capacitor.
Further, in order to prevent damage to the analog capacitor due to a high applied voltage, it is necessary to develop a material having a high breakdown voltage while suppressing a leakage current.